Reduction of Hydrodynamic Noise of 3D Hydrofoil with Spanwise Microgrooved Surfaces Inspired by Sharkskin

Abstract

Loud hydrodynamic noise is not only potentially harmful to the health of organisms in the ocean, but it is also a threat to the survival of underwater vehicles. Different from the general noise reduction technologies at present, a new idea for a flow-induced noise reduction design with spanwise microgrooved surfaces inspired by sharkskin is introduced in this paper. Large eddy simulations (LES) combined with the Ffowcs Williams and Hawkings (FW-H) equation are adopted to simulate the hydrodynamic noise of the three-dimensional (3D) hydrofoil. The accuracy of the numerical predictions is checked against existing experimental data, achieving good agreement. With the increase of observing distance, the noise reduction effect at the trailing edge direction is gradually apparent, and a maximum noise reduction of up to 7.28 dB can be observed. It is seen from the noise spectra of the biomimetic hydrofoil that the main peaks are eliminated, and the noise level at high frequency is also decreased. The cause of noise reduction lies in the secondary vortex generated in the microgrooves, which hinder the process of turbulence, consume the energy of the flow, and weaken the intensity of turbulent burst. The results of this study provide a new way to design low-noise underwater structures with hydrofoils.

Noise Characteristics Analysis of the Horizontal Axis Hydrokinetic Turbine Designed for Unmanned Underwater Mooring Platforms

“…Like wind turbines, the vertical axis turbines are much quieter compared with the horizontal types, and the horizontal axis turbines often generate low-frequency noise at blade passing frequency and higher order harmonics, which are harmful to the environment [17]. This phenomenon has also been confirmed by the research group from Northwestern Polytechnical University, with a series of continuous research [4,5,7,8,18]. In fact, the HAHT investigated in this paper and the horizontal axis wind turbines are similar to the rotating machinery of renewable energy.…”

Review of Computational Fluid Dynamics Analysis in Biomimetic Applications for Underwater Vehicles

“…Moreover, they found that at higher inflow speeds, this design is more effective in suppressing lift fluctuations and reducing noise. Dang et al [192] achieved further advancements in noise reduction technologies for underwater vehicles by developing a transverse micro-groove surface, inspired by the texture of shark skin. This innovative surface, as depicted in Figure 20, was specifically designed to reduce the hydrodynamic noise of hydrofoils.…”

Thriving artificial underwater drag-reduction materials inspired from aquatic animals: progresses and challenges

“…This explanation has been later corroborated. 84 The suppression of lateral fluctuations and the capture of small-scale vortices are used to explain the drag reduction of the riblets; 85 also, the complexity of the shark scales is considered to be due to the simplified riblet only, which implied drag reduction mechanism; thus, real and highly similar shark skins, whose surface is covered by denticles, have also been hydrodynamically tested to explain the reason for shark skin drag reduction.…”

“…The structure of spanwise riblet inspired by sharkskin has been applied to simulate the hydrodynamic noise of the three-dimensional (3D) hydrofoil and the maximum noise reduction was observed at 7.28 dB. 84 The blade bionic groove design proposed by J. Wang, Nakata, and Liu 203 was applied to the mixed flow fan and it was found that the use of the groove structure has the potential to suppress noise. When the aerodynamic efficiency loss is only 0.3 percentage points, the blade leading edge reduces the turbulent flow energy by about 38%.…”